Effect of Ce doping and oxygen deficiency in Nd_2-xCe_xCuO_4-y

Electrical resistivity and magnetoresistance of the as-grown and reduced single crystals of Nd_2-xCe_xCuO_4-y have been measured in order to clarify the effect of the Ce doping and the oxygen deficiency on the conduction. The resistivity of the as-grown samples is metallic at high temperatures, but shows tendency toward localization at low temperatures. The as-grown samples without reduction do not show superconductivity. We found that the Ce doping increases the number of the electron carriers and causes the random potential as well. Oxygen deficiency is understood to increase the number of the electron carriers without causing the random potential and raise the Fermi level up to the mobility edge from in the localized states.